Choosing a Planted Aquarium Substrate

Not all substrates are created equal, especially if you intend to grow plants in them. There are many things to consider, particle size, color, nutrient content, price, species of fish, etc… Selecting a substrate when you’re setting up a planted aquarium can seem daunting at first, but hopefully after reading through this you will learn enough that you can make an informed decision on what will work best for you.

Do you need a substrate

First things first, you don’t even necessarily need a substrate to grow plants. Many plants can be grown on rocks or driftwood(and may prefer or require it), such as Anubis or Java Fern. If you just plan on growing one or two plants you could always grow them in pots in the aquarium, but if you plan on having many plants or are going for a more natural look you may want to consider a substrate.

Particle size

Particle size is very important, very compact substrates(such as fine sands) leave very little space between particles, this makes it hard for plant roots to penetrate into them and therefore limits root growth.  Dense or very deep substrates also can lead to anaerobic zones, which are areas where oxygen in the water doesn’t reach. These zones can produce hydrogen sulfide, which can build up and dissipate into the tank, which is a problem as this gas is toxic to fish.

Too large of substrate particles can also be an issue. Food and waste tends to settle in coarse gravel, which is less than ideal. On top of that particles that are too large can block roots. Ideally you are looking for a substrate with particles between 3 and 8mm.

The type of fish you keep will also dictate what type of substrate you can use. Softer substrates are required for scaleless fish such as Khuli Loaches or with barbells such as Corydoras.

pH and hardness

Many substrates will have a chemical reaction with your water. Some will lower the pH of the water(peat moss) and others will raise it(aragonite, onyx), do research on the specific brand you intend to use so you are not caught off guard. Over time these effects will lessen and you will need to add more substrate if you intend to maintain pH’s different than what your water is.

Many aragonite or onyx substrates will also make your water harder, which most plants don’t like and are not recommended for a traditional planted tank unless you are doing specific aquarium plants for this.

Nutrients

Some substrates are very nutrient poor (sand, gravel, etc…), these aren’t an ideal choice for a planted tank as many plants absorb their nutrients through their roots. Other substrates are very rich in nutrients (soil, clay, etc…), which are the more traditional choices for a planted tank. These substrates do decrease in their nutrient levels over time and regardless of which type of substrate you choose you will want to supplement for the nutrient demand of your plants with fertilizers and root tabs.

A side note with soil based substrates is that they often release ammonia when first introduced into an aquarium. This is great for kicking off the cycling process of your tank, but not so great for fish.

Layers & Depth

Nutrient rich substrates tend to cost more than gravel or sand options. If your budget is tight it is an option to use gravel as a bottom layer and a higher quality nutrient rich substrate as a top layer.

Ideally you will have a substrate at least 1″ to 2″ and as long as the substrate isn’t to fine you can go up to 4″. This allows for large healthy root systems to grow for your plants.

Common Choices

These are some common choices that are often used in planted tanks. All of these I would use personally in my tanks, and if you are so inclined you can support this site by using these links.

CarribSea Ecco Complete

This is the current substrate in my personal planted tank:

  • Complete substrate for freshwater planted aquariums
  • Contains major and minor trace elements to nourish aquarium plants
  • Substrate encourages healthy plant root growth

CaribSea Eco-Complete 20-Pound Planted Aquarium, Black

Flourite

The substrate I used on my old planted tank back in the day:

  • Mineral rich volcanic soil
  • Stimulates strong plant growth
  • Promotes neutral to mildly acidic pH
  • Suitable for plants or shrimp

Flourite Dark, 7 kg / 15.4 lbs

Fluval Plant and Shrimp Stratum

  • Mineral rich volcanic soil
  • Stimulates strong plant growth
  • Promotes neutral to mildly acidic pH
  • Suitable for plants or shrimp

Fluval Plant and Shrimp Stratum, 4.4-Pound

ADA Aqua Soil Amazonia

  • Helps to bring the pH level of the water down to an ideal level for most of the aquatic plants.
  • Gives clarity to the water and creates conditions ideal for healthy growth of aquatic plants.
  • Composed of granules of size and density ideal for the fast development of healthy plant root systems, rather conventional substrates such as sand.
  • Helps to lower the hardness level of the water.

ADA Aqua Soil Amazonia (3 Liter/ Approx 7 Lbs) Normal Type

Conclusion

There are many things to consider when choosing a substrate for your planted aquarium. With proper maintenance, fertilizers, and stocking you can go a long way using just about anything, but it definitely can be a major help to pick the right one to start your tank with and give you a head start, especially if you’re new to all this.

Hopefully this helped make sense of the issue for you. Feel free to share it with anyone who needs assistance and hopefully your planted tank grows in nicely.

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